Fuel shutoff device for internal combustion engine

ABSTRACT

A fuel shutoff device adapted for incorporation into an automobile fuel supply system as to shut off the fuel supply during deceleration thereby reducing the amount of carbon monoxide and hydrocarbons emitted in exhaust. A throttle valve position detector is operatively associated with a throttle valve so as to produce a voltage signal corresponding to the position of the throttle valve. The voltage signal is applied to a fuel shutoff signal generator which generates a fuel shutoff signal when the time derivative of the voltage signal exceeds a predetermined value. The fuel shutoff signal is applied to a shutoff valve controller which is actuated to close a shutoff valve when the fuel shutoff signal is applied to the controller. The fuel shutoff signal is also applied to a fuel shutoff controller which de-energizes an injection pulse amplifying circuit when the fuel shutoff signal is applied to the controller. The present fuel shutoff device further includes a throttle valve switch which is adapted to be closed when the throttle valve is moved to its fully closed position. The throttle valve switch is connected to the shutoff valve controller. An engine driven triggering device which generates a signal indicating engine speed also is connected to the shutoff valve controller. Operation of the shutoff valve controller is such that with the throttle valve switch closed, when the engine speed rises to a first predetermined level, for example, 2000 rpm, the controller operates in such a manner as to close the shutoff valve. Further, with the throttle valve switch closed, when the engine speed decreases to a second predetermined level, for example, 1000 rpm, the shutoff valve is reopened by the controller. Since, in the present fuel shutoff device, the fuel supply to the cylinders is shut off during deceleration before the throttle valve is reached to its fully closed position, the amount of carbon monoxide and hydrocarbon exhaust is small in comparison with an automobile employing a conventional fuel shutoff device.

United States Patent 3,703,162 Nov. 2i, 1972 Aono 1541 FUEL SHUTOFF DEVICE FOR INTERNAL COMBUSTION ENGINE [72] Inventor: Shigeo Aono, Yokosuka, Japan [73] Assignee: Nissan Motor Company, Limited, Yokohama, Japan [22] Filed: Oct. 31, 1970 21 App1.No.: 80,439

[52] U.S. Cl. ..123/32 EA, 123/97 B, 123/119 R [51] Int. Cl ..F02b 3/00, F02d 31/00, F02b 33/00 [58] Field of Search ..l23/32, 32 EL, 97 B [56] References Cited UNITED STATES PATENTS 2,911,966 11/1959 Pribble ..l23/32 EL 3,051,152 8/1962 Paule ..123/32 EL 3,272,187 9/1966 Westbrook ..l23/32 EL 3,407,793 10/1968 Lang ..l23/32 EL 3,430,616 3/1969 Glockler ..123/32 EL 3,463,130 8/1969 Reichardt ..l23/32 EL 3,470,854 .10/1969 Eisele ..123/32 EL 3,504,657 5/1970 Eichler ..123/32 EL 3,522,794 8/1970 Reichardt ..l23/32 EL 3,548,792 12/1970 Palmer ..l23/32 EL 3,570,460 3/1971 Rabus ..l23/32 EL Primary Examiner-Laurence M. Goodridge Assistant Examiner-Ronald B. Cox Attorney-McCarthy, Depaoli, OBrien & Price [57] ABSTRACT A fuel shutoff device adapted for incorporation into an automobile fuel supply system as to shut off the fuel supply during deceleration thereby reducing the amount of carbon monoxide and hydrocarbons emitted in exhaust. A throttle valve position detector is operatively associated with a throttle valve so as to produce a voltage signal corresponding to the position of the throttle valve. The voltage signal is applied to a fuel shutoff signal generator which generates a fuel shutoff signal when the time derivative of the voltage signal exceeds a predetermined value. The fuel shutoff signal is applied to a shutoff valve controller which is actuated to close a shutoff valve when the fuel shutoff signal is applied to the controller. The fuel shutoff signal is also applied to a fuel shutoff controller which de-energizes an injection pulse amplifying circuit when the fuel shutoff signal is applied to the controller. The present fuel shutoff device further includes a throttle valve switch which is adapted to be closed when the throttle valve is moved to its fully closed position. The throttle valve switch is connected to the shutoff valve controller. An engine driven triggering device which generates a signal indicating engine speed also is connected to the shutoff valve controller. Operation of the shutoff valve controller is such that with the throttle valve switch closed, when the engine speed rises to a first predetermined level, for example, 2000 rpm, the controller operates in such a manner as to close the shutoff valve. Further, with the throttle valve switch closed, when the engine speed decreases to a second predetermined level, for example, 1000 rpm, the shutoff valve is reopened by the controller. Since, in the present fuel shutoff device, the fuel sup ply to the cylinders is shut off durmg deceleration be ore the throttle valve is reached to its fully closed position, the amount of carbon monoxide and hydrocarbon exhaust is small in comparison with an automobile employing a conventional fuel shutoff device.

10 Claims, 9 Drawing Figures SHUTOF F VALVE CONTROLLER SHUTOF F GENERATOR l I I l COMPUTING FUEL SHUTOFF CONTROLLER CIRCUlT PATENTED am: 2 1 I972 SHEU 1 OF 7 INVENTOR SHIGEO AONO ATTORNEYS PKIENTEDNMI I 1 3.703.162

I SHEET 2 UF 7 Ci W x 2 a 10 i 20 I DC OUTPUT T 1 DC OUTPUT I 1: I; I

INVENTOR 8 SH 16 50 A 0 N O ATTORNEYS PATENTED am 2 1 1912 SHEET 6 BF 7 TIME, t,

INVENTOR SH/G E0 AONO @MM, M2675;

ATTORNEYS FUEL SHUTOFF DEVICE FOR INTERNAL COMBUSTION ENGINE This invention relates generally to a fuel system for an internal combustion engine and more particularly to a device adapted for incorporation into such a system as to shut off the fuel supply during deceleration thereby reducing the amount of carbon monoxide and hydrocarbons emitted in automobile exhaust.

Now that air pollution caused by automobile exhaust emissions is posing serious social problems, the development of pollution-free cars is a matter of primary consideration with most automobile manufacturers. Among various anti-pollution measures now being adopted by them is one which shuts off the fuel supply to the cylinders during deceleration, which is effective in reducing carbon monoxide and hydrocarbons in exhaust considerably. In the ordinary fuel shutoff device for an automobile internal combustion engine, a shutoff valve is actuated to shut off the fuel supply by detecting the existence of one of the following two conditions:

1. When the intake manifold pressure is above a predetermined value; and

2. When the relationship between engine speed and throttle valve position falls within a predetermined range.

However, such a fuel shutoff device operates in such a manner as to close the shutoff valve when the throttle valve is reached to its fully closed position, with the result that there is still a considerable amount of the pollutants remaining.

This invention features a new and improved fuel shut-off device for an automobile internal combustion engine comprising first means operatively associated with a throttle valve to generate a voltage signal corresponding to the position of the throttle valve, second means connected to said first means to generate a fuel shutoff signal when the time derivative of the voltage signal exceeds a predetermined value, and third means responsive to the fuel shutoff signal to shut off the fuel supply to the cylinders.

It is therefore an object of this invention to provide a fuel shutoff device which is adapted for incorporation into an automobile fuel supply system as to shut off the fuel supply during deceleration thereby reducing carbon monoxide and hydrocarbon contents in exhaust gases remarkably.

It is another object of this invention to provide a fuel shutoff device in which during deceleration before the throttle valve is reached to its fully closed position a fuel shutoff signal is generated to close the shutoff valve.

It is a further object of this invention to provide a fuel shutoff device suitable for use in a fuel injection system and which de-energize an injection pulse drive during the time that the fuel shutoff signal is applied thereto.

It is yet a further object of this invention to provide a fuel shutoff device suitable for use in a carburettor-type fuel system and which is simple in construction.

In the drawings:

FIG. 1 is a schematic diagram showing a fuel shutoff device of this invention as incorporated into a conventional fuel injection system;

FIG. 2 is a schematic diagram showing an example of a throttle valve position detector employed in the fuel shutoff device of FIG. 1;

FIG. 3. is a circuit diagram of another arrangement of the throttle valve position detector;

FIG. 4 is a circuit diagram of a fuel shutoff signal generator shown in FIG. 1;

FIGS. 5(a) to (c) diagrammatically show throttle valve position, velocity of movement of the throttle valve, and fuel shutoff signal;

FIG. 6 is a circuit diagram of shutoff valve controller shown in FIG. 1;

FIG. 7 shows an injection pulse drive circuit of the fuel injection system shown in FIG. 1;

FIGS. 8(a) to (e) diagrammatically show the extent to which the amount of carbon monoxide and hydrocarbon exhaust is reduced by the fuel shutoff device of this invention; and

FIG. 9 is a view similar to FIG. 1, but shows the present shutoff device when applied to a carburettortype fuel supply system.

Referring to the drawings and more particularly to FIG. 1, a fuel injection system having a fuel shutoff device according to one embodiment of this invention is shown. In the figure, numeral 10 designates a throttle valve adapted to be tilted in an throttle chamber 11 to allow more or less air to flow therethrough. The throttle chamber 11 communicates with an intake manifold 12 mounted on the side of a cylinder block 13. A fuel injection nozzle 14 is mounted in the intake manifold 12 to inject fuel in a sprayed form. While the nozzle is shown as located in the intake manifold it is to be understood that the nozzle could equally as well be located to inject directly into the cylinder of the engine downstream of the intake valve. Although not shown, a pump is adapted to deliver fuel under pressure from a source to a pressure regulator which controls the pressure of the fuel supplied to the nozzle. The fuel issuing from the pressure regulator is passed through a shutoff valve 15 to the nozzle 14 which is controlled by a solenoid actuated valve 16.

The throttle valve 10 is operatively associated with an accelerator pedal in the drivers compartment through a mechanical linkage (not shown). Mounted in the mechanical linkage is a throttle valve switch 21 which is adapted to be closed when the throttle valve 10 is moved to its fully closed position. Also mounted in the mechanical linkage is a throttle valve position detector 17 which produces a dc. voltage signal corresponding to the position of the throttle valve 10. FIG. 2 diagrammatically shows one such example of the throttle valve position detector 17 containing a sliding contact 18 that slides back and forth on a resistance 19 as the throttle valve 10 is opened and closed. The resistance 19 has its one end connected to a constant voltage source such as a battery 20 and the other end grounded. The dc. voltage corresponding to the throttle valve position is derived from the sliding contact 18. The switch which is closed in response to closure of the throttle valve is indicated at 21 in FIG. 2.

FIG. 3 diagrammatically shows another embodiment of the throttle valve position detector 17. The left-hand half portion of the circuit shown, which comprises a transistor 22, is an oscillation circuit having a constant oscillation frequency. The output of the oscillation circuit is derived from an inductance coil 23 which is coupled to another inductance coil 24, with a shielding plate 25 positioned therebetween. The shielding plate 25 is operatively associated with the mechanical linkage in such a manner as to give minimum shiedling when the accelerator pedal is fully depressed, that is, the throttle valve is fully opened. The inductance coil 24 provides an input power to a d.c. conversion circuit including a transistor 26, which circuit converts the input power provided by the inductance coil 24 into d.c. voltage corresponding thereto. Thus, a d.c. voltage E which depends upon the throttle valve position is derived from an output terminal 27 of the conversion circuit.

Turning back to FIG. 1, the d.c. voltage signal corresponding to the throttle valve position is applied to a fuel shutoff signal generator 30, the function of which is to differentiate the d.c. voltage E and to produce a fuel shutoff signal when the absolute value of the time derivative dE/dt exceeds a predetermined value. Since the time derivative dE/dt is proportional to the velocity of movement of the throttle valve 10, the fuel shutoff signal is produced when the velocity with which the throttle valve returns toward its fully closed position exceeds a predetermined value.

The fuel shutoff signal is applied to a shutoff valve controller 31, the output of which is connected to the shutoff valve 15. The controller 31, in response to the fuel shutoff signal, operates in such a manner as to keep the shutoff valve closed thereby interrupting delivery of fuel from the pressure regulator to the injection nozzle 14. in addition to the fuel shutoff signal passed from the throttle valve position detector 17, the shutoff valve controller 31 receives two signals indicating engine speed and full closure of throttle valve 10, respectively. The engine speed is sensed by an engine driven triggering device 32, as shown in the left-hand portion of FIG. 1, which device is incorporated in a distributor housing (not shown). The device 32 comprises a cam 33 mounted on an engine driven shaft 34 and two triggering switches 35 and 36 adapted to be altemately actuated by rotation of the cam 33 in dependence on engine speed. The stationary contacts 37 and 33 of the triggering switches 35 and 36 are connected to a battery 39 through resistors 40 and 41, respectively, and also to the shutoff valve controller 31. Thus, when the cam 33 is rotated by the engine in dependence on engine speed, a pulse signal having a repetition rate proportional to the engine speed is supplied from the engine driven triggering device 32 to the shutoff valve controller 31. The fuel closure of the throttle valve 10 is detected by the switch 21, (FIGS. 2 and 3) which is operatively associated with the mechanical linkage as described above. The operation of the controller 31 in terms of engine speed and full closure of the throttle valve 10 will be fully described hereinafter.

The pulse signal indicating engine speed is applied also to an computing circuit 42 which, in response to the engine speed and other engine operating conditions such as intake manifold pressure and engine temperature, calculates a proper pulse width of an injection pulse which actuates the injection valve 16. The injection pulse from the computing circuit 42 is passed through a fuel shutoff controller 43 to each of the solenoid actuated injection valve 16. The fuel shutoff controller 43 is connected to the shutoff signal generator 30 by means of a lead 44 so that in response to the fuel shutoff signal the controller 43 is gated off, allowing no injection pulse to be transmitted to the injection valve 16. Therefore, it is to be noted that when a fuel shutoff signal is generated the injection valve 16 is closed simultaneously with closure of the shutoff valve 15.

FIG. 4 shows an example circuit of the fuel shutoff signal generator 30 shown in FIG. 1. The circuit is a monostable multivibrator having connected to the input thereof a differentiating circuit consisting of a capacitor and a resistor 51. Connected at a joint 52 between the capacitor 50 and resistor 51 is a diode 53 which in turn is connected to the collector of a normally nonconducting transistor 54. The diode 53 is polarized in a direction to allow only negative-going pulse to be transmitted therethrough. The collector of the transistor 54 is connected via a capacitor 55 to the base of a normally conducting transistor 56 whose collector is connected via a resistor 57 to the base of the normally nonconducting transistor 54. The resistor 51 is connected to a bus line 58 connected to a battery. The collector of the normally nonconducting transistor 54 and the base and collector of the normally conducting transistor 56 are connected to the bus line 58 by way of resistors 59, 60 and 61, respectively. The emitters of the two transistors 54 and 56 are connected directly to ground. The fuel shutoff signal is derived from the collector of the normally conducting transistor 56.

Operation of the shutoff signal generator 30 shown in FIG. 4 is such that when the throttle valve 16 returns toward its fully closed position a negative voltage whose magnitude is proportional to the velocity of the throttle movement is at the joint 52 between the capacitor 51 and the resistor 51. The negative voltage is applied through the diode 53 and the capacitor 55 to the base of the normally conducting transistor 56. As shown in FIGS. 5(a), (b) and (0), when the velocity with which the throttle valve 10 returns toward its fully closed position exceeds a predetermined level which corresponds to the threshold voltage of the transistor $6, it is rendered nonconductive, causing the transistor 54 to become conductive. The multivibrator is now in its quasi-stable state, producing an output signal at the collector of the normally conducting transistor 56. The circuit will remain in the quasi-stable state for only a definite duration T which is dependent upon the values of the capacitor 55 and the resistor 61). The duration T is set to be long enough so that until the throttle valve 10 reaches the fully closed position there still remains the output voltage at the collector of the transistor 56, as shown in FIG. 5(a). Upon termination of the definite time duration a regenerative action will take place, rendering the transistor 56 conductive and eventually returning the multivibrator to its initial stable state.

The output signal from the collector of the transistor 56 is supplied to a driving circuit including a resistor 69 and a normally nonconducting transistor 71 in the shutoff valve controller 31 shown in FIG. 6. Upon application of the fuel shutoff signal to the base of the transistor 71 it is rendered conductive, causing the shutoff valve 15 to be closed to interrupt fuel delivery to the injection nozzle 14.

Shown in the lower left-hand portion of FIG. 6 is an input terminal 7 2 of the circuit, which is connected to the engine driven triggering device 32 (FIG. 1) so that a pulse signal indicating engine speed is applied to the circuit. A differentiating circuit comprising a capacitor 73 and a resistor 74 is connected to the input terminal 72 as shown. A diode 75 is connected to the junction between the capacitor 73 and the resistor 74 and is polarized in a direction to allow only a positive-going pulse to be transmitted therethrough. The diode 75 is also connected to an integrator comprising a resistor 76 and a capacitor 77, the junction between which is connected to the base of a transistor 78. Thus, a d.c. voltage proportional to engine speed is applied to the base of the transistor 78. The transistor 78 has its collector connected to a bus line 79 via a resistor 80 and its emitter grounded by way of a resistor 81. The base of the transistor 78 is connected via a resistor 82 to a voltage divider consisting of two resistors 83 and 84 which are connected between the bus line 79 and ground. The resistance valves of the four resistors 81, 82, 83 and 84 are adjusted so that when the base potential of the transistor 78 exceeds a value corresponding to a first predetermined engine speed such as 2000 rpm the transistor 78 is rendered conductive.

The diode 75 is connected also to another integrating circuit comprising a resistor 85 and a capacitor 86, the junction between which is connected to the base of a transistor 87. Like the transistor 78, the transistor 87 has its collector connected via a resistor 88 to the bus line 79 and its emitter connected via a resistor 89 to ground. The base of the transistor 87 is connected by way of a resistor 90 to a voltage divider comprising two resistors 91 and 92. The four resistors 89, 90, 91 and 92 are adjusted so that when the potential at the base of the transistor 87 rises to a value corresponding to a second predetermined engine speed such as 1000 rpm the transistor 87 is rendered conductive.

The collector of the transistor 78 is connected to the collector of a normally nonconducting transistor 93 by way of a capacitor 94 and a diode 95. The diode 95 is polarized in a direction to allow only a negative-going pulse to be transmitted therethrough. The transistor 93 has its collector connected via a resistor 96 to the base of a normally conducting transistor 97 which forms a flip-flop together with the transistor 93. The base of the transistor 93 is connected via a resistor 99 to the collector of the normally conducting transistor 97, which collector is connected to the bus line 79 by way of a resistor 100. The bases of the two transistors 93 and 97 are connected to ground by way of resistors 101 and 102, respectively. The emitters of the two transistors 93 and 97 are connected together to ground by way of a parallel connection of a resistor 103 and a capacitor 104. The base of the normally conducting transistor 97 is connected to the bus line 79 via a diode 105 and two serially connected resistors 106 and 107. Connected to the junction between the two resistors 106 and 107 is the switch 21 (FIGS. 2 and 3) which is operatively associated with the throttle valve in such a manner as to be closed when the throttle valve 10 is reached to its fully closed position. The switch 21 is also connected to ground. The collector of the transistor 87 is connected to the base of the normally conducting transistor 97 by way of a capacitor 108 and a diode 109 which is polarized in a direction to allow only a positive-going pulse to be transmitted therethrough. The normally conducting transistor 97 of the flip-flop has its collector connected via a resistor 110 to the base of the transistor 71.

In the operation of the above-described shutoff valve controller 31, when the switch 21 is kept open, that is,

- when the throttle valve 10 is not in its fully closed position, the flip-flop is maintained in its first stable state with the transistors 93 and 97 nonconducting and conducting, respectively, since the base of the transistor 97 is connected to the bus line 79 through the resistors 106 and 107 and the diode 105. With the transistor 97 conducting, the voltage at the collector thereof, which voltage is applied to the base of the transistor 71, is not sufficiently high to render it conductive. Thus, the current path from the bus line 79 through the solenoid actuated shutoff valve 15 to ground is not established. Under these conditions, if the switch 21 is closed, a negative-going pulse is generated at the junction between the resistors 106 and 107, which pulse, however, is prevented from being transmitted to the base of the transistor 97 by the diode 105.

When the engine speed rises above the second predetermined speed such as 1000 rpm, the transistor 87 is rendered conductive to generate a negative-going pulse at the collector thereof. However, the negativegoing pulse has no effect upon the flip-flop since the pulse is prevented from passing through the diode 109. When the engine speed further increases, exceeding the first predetermined speed such as 2000 rpm, the transistor 78 is rendered conductive to develop at the collector thereof a negative-going pulse which in turn is passed through the capacitor 94 and the diode to the collector of the normally nonconducting transistor 93 and hence to the base of the normally conducting transistor 97 by way of the resistor 96. Thus, if the throttle valve switch 21 is closed, the negative-going pulse renders the transistor 97 nonconductive, driving the flip-flop to its second state in which the increased voltage at the collector of the transistor 97 is applied to the base of the transistor 71, rendering it conductive thereby actuating the shutoff valve 15.

Conversely, when the engine speed decreases to the first predetermined speed, the transistor 78 is rendered nonconductive, generating a positive-going pulse at the collector thereof. However, this pulse is prevented from passing through the diode 95. When the engine speed drops further to the second predetermined speed, the transistor 87 is rendered nonconductive to develop a positive-going pulse at the collector thereof. The positive-going pulse, however, is permitted to pass the capacitor 108 and the diode 109 to the base of the transistor 97 rendering it conductive and eventually rendering the transistor 93 non-conductive, so that the shutoff valve 15 ceases from interrupting delivery of fuel to the injection nozzle 14. It should be understood from the foregoing that if the switch 21 is not closed the flip-flop remains in its first stable state while when the switch 21 is not closed the flip-flop is under the influence of the output pulses from the transistors 78 and 87.

FIG. 7 shows an example of the fuel shutoff controller 43 shown in FIG. 1, which is adapted to receive an injection pulse signal from the computing circuit 42 and amplify the signal to actuate the solenoid actuated injection valve 16. The injection pulse signal is applied to an input terminal 111 which is connected via a resistor 112 to the base of a transistor 113. The transistor 113 has its collector connected via a resistor 114 to a bus line 115 and its emitter grounded. The collector is connected via a resistor 116 to the base of a transistor 117 having its collector connected via a resistor118 to the bus line 115 and its emitter grounded. The collector of the transistor 117 is connected to the base of a transistor 119 whose emitter is grounded. The collector of the transistor 119 is connected to the bus line 115 by way of two serially connected resistor 120 and 121, the junction between which is connected to the base of a transistor 122, the emitter thereof being connected to the bus line 115. The collector of the transistor 122 is connected to ground by way of a capacitor 123 and a resistor 124. One solenoid actuated injection valve 16, is shown as shunting the series connection of the capacitor 123 and the resistor 124.

Connected to the base of the transistor 113 of the first amplifying stage is the collector of a transistor 125, the emitter thereof being grounded. The base of the transistor 125 is connected to the output terminal of shutoff signal generator 30. In the absence of the fuel shutoff signal at the base of the transistor 125, it is kept nonconductive so that an injection pulse generated by the computing circuit 42 is applied to the base of the transistor 113 and is amplified by the transistor 113 and the following three transistors 117, 119 and 122. The injection pulse thus amplified actuates the injection valve 16 to discharge fuel into the intake manifold 12. However, when the fuel shutoff signal is applied to the transistor 125, it is rendered conductive, causing the base potential of the transistor 113 to drop to zero; As a result, the injection pulse signal applied to the circuit is interrupted, so that the injection valve 16 is not actuated.

FIGS. 8(a) to (e) illustratively shows how the amount of carbon monoxide and hydrocarbons emitted in automobile exhaust is reduced by the use of the present fuel shutoff device. In FIGS. 8(d) and (c), the solid lines 126 and 127 represent the levels of emission of the carbon monoxide and hydrocarbons, respectively, measured when the present fuel shutoff device is used, while the dotted lines 128 and 129 represent those measured when a conventional fuel shutoff device is used.

FIG. 9 diagrammatically shows another embodiment of the present fuel shutoff device when it is applied to a carburettor-type fuel system. In the figure, numeral 130 designates a solenoid actuated valve adapted to open and close the idle and low-speed passage 131 of the carburettor 132. The throttle valve is linked to a throttle valve position detector of variable resistor type 17 shown in FIG. 2. The sliding contact 18 of the detector 17 is connected to a shutoff signal generator 30 as shown in FIG. 4. The output of the generator 30 is connected to a shutoff valve controller 31 of the type shown in FIG. 6. The shutoff valve controller 31 also receives a pulse signal indicating engine speed from an engine driven triggering device 32 as shown in FIG. 1. The output of the shutoff valve controller 31 is connected to the solenoid actuated shutoff valve 130 so that in response to the fuel shutoff signal from the fuel shutoff signal generator 30 the valve 130 is actuated to close the passage through the idle and low-speed passage 131. Although not shown, the fuel shutoff device also includes a switch 21 which is closed when the throttle valve 10 is moved to its fully closed position. The throttle valve switch 21 is connected to the fuel shutoff controller 31. The operation of this fuel shutoff device in terms of engine speed and movement of the throttle valve switch 21 is the same as that described in conjunction with FIG. 6.

What is claimed is:

1. A fuel shutoff device for an internal combustion engine having throttle valve and adapted for shutting off the fuel supply to said engine during deceleration to reduce carbon monoxide and hydrocarbon contents in exhaust gases emitted from said engine, said fuel shutoff device comprising, in combination, a throttle valve position detector having means operatively associated with said throttle valve for generating a voltage signal corresponding to the position of said throttle valve, a fuel shutoff signal generator responsive to said voltage signal from said throttle valve position detector for generating a fuel shutoff signal, said fuel shutoff signal generator including a differentiating circuit connected to said throttle valve position detector for receiving said voltage signal corresponding to the position of said throttle valve and a monostable multivibrator connected to said differentiating circuit for generating said fuel shutoff signal, said differentiating circuit having means for differentiating said voltage signal in terms of time to render said monostable multivibrator in its quasi-stable state to cause the same to generate said fuel shutoff signal when the time derivative of said voltage signal exceeds a predetermined value during said deceleration, said monostable multivibrator having means to keep the time duration during which said monostable multiple vibrator remains in its quasi-stable state to be long enough to last still after said throttle valve reaches its fully closed position, and a shutoff valve controller connected to said fuel shutoff signal generator and responsive to said fuel shutoff signal to shut off the fuel supply to said engine.

2. A fuel shutoff device for an internal combustion engine having a throttle valve and adapted for shutting off the fuel supply to said engine during deceleration to reduce carbon monoxide and hydrocarbon contents in exhaust gases emitted from said engine, said fuel shutoff device comprising, in combination, a throttle valve position detector operatively associated with said throttle valve for generating a voltage signal in proportion to the position of said throttle valve, said throttle valve position detector having an oscillation circuit with a constant oscillation frequency and a d.c. conversion circuit to receive the output of said oscillation circuit by way of a coupling coil, the degree of said coupling coil being changed by a shielding plate which moves as said throttle valve is moved, a fuel shutoff signal generator responsive to said voltage signal from said throttle valve position detector for generating a fuel shutoff signal, said fuel shutoff signal generator including a differentiating circuit connected to said throttle valve position detector for receiving said voltage signal and a monostable multivibrator connected to said differentiating circuit for generating said fuel shutoff signal in response to the output thereof, said differentiating circuit having means for differentiating said voltage signal in terms of time to render said monostable multivibrator in its quasi-stable state when the time derivative of said voltage signal exceeds a predetermined value during said deceleration, said monostable multivibrator having means to keep the time duration during which said monostable multivibrator remains in its quasi-stable state to be long enough to last still after said throttle valve reaches its fully closed position, and a shutoff valve controller connected to said fuel shutoff signal generator and responsive to said fuel shutoff signal to shut off the fuel supply to said engine.

3. A fuel shutoff device according to claim 2 wherein said differentiating means includes a capacitor connected to said throttle valve position detector and a resistor connected to said capacitor, the joint between said capacitor and said resistor being connected to said monostable multivibrator.

4. A fuel shutoff device according to claim 2, wherein said means of said monostable multivibrator includes a capacitor and a resistor connected thereto.

5. A fuel shutofi device for an internal combustion engine having a throttle valve and adapted for shutting off the fuel supply to said engine during deceleration thereof to reduce carbon monoxide and hydrocarbon contents in exhaust gases emitted from said engine, said fuel shutoff device comprising, in combination, a fuel shutoff valve, a throttle valve position detector operatively associated with said throttle valve for generating a voltage signal in proportion to the position of said throttle valve, a fuel shutoff signal generator responsive to said voltage signal for generating a fuel shutoff signal, said fuel shutoff signal generator including a differentiating circuit connected to said throttle valve position detector for receiving said voltage signal and a monostable multivibrator connected to said differentiating circuit for generating said fuel shutoff signal in response to the output thereof, said differentiating circuit having means for differentiating said voltage signal in terms of time to render said monostable multivibrator in its quasi-stable state when the time derivative of said voltage signal exceeds a predetermined value during said deceleration, said monostable multivibrator having means to keep the time duration during which said monostable multivibrator remains in its quasi-stable state to be long enough to last still after said throttle valve reaches to its fully closed position, an engine driven triggering device having means for producing a pulse signal having a repetition rate proportional to engine speed, a fully closed throttle valve detecting switch adapted to be closed when said throttle valve is moved to its fully closed position, a shutoff valve controller having a plurality of inputs connected to said fuel shutoff signal generator, said engine driven triggering device and said fully closed throttle valve detecting switch and an output connected to said fuel shutoff valve, said shutoff valve controller being responsive to said fuel shutoff signal for thereby keeping said shutoff valve closed to interrupt delivery of fuel to said engine.

6. A fuel shutoff device according to claim 5, wherein said throttle valve position detector includes an oscillation circuit having a constant oscillation frequency and dc. conversion circuit adapted to receive the output of said oscillation circuit by way of a coupling coil, the degree of coupling of said coupling coil being changed by a shielding plate which moves as said throttle valve is moved.

7. A fuel shutoff device according to claim 6,

wherein said shutoff valve controller includes a driving circuit having an input connected to said fuel shutoff signal generator and an output connected to said shutoff valve, first and second switching circuits connected to said engine driven triggering device, said first switching circuit being responsive when said pulse signal exceeds a value corresponding to a first predetermined engine speed, and said second switching circuit being responsive when said pulse signal exceeds a value corresponding to a second predetermined engine speed, and a flip-flop circuit having a plurality of inputs connected to said first and second switching circuits and said fully closed throttle valve detecting switch and having an output connected to said driving circuit for controlling said driving circuit in response to said pulse signal and the output from said fully closed throttle valve detecting switch for thereby controlling actuation of said shutoff valve.

8. A fuel shutoff device according to claim 6, further comprising a fuel injection valve communicating with said fuel shutoff valve, a computing circuit connected to said engine driven triggering device to calculate a proper pulse width of an injection pulse for actuating said fuel injection valve in response to said pulse signal from said engine driven triggering device, and a fuel shutoff controller having inputs connected to said computing circuit and said fuel shutoff signal generator and an output connected to said fuel injection valve, said fuel shutoff controller being responsive to said fuel shutoff signal for thereby closing said fuel injection valve simultaneously with said fuel shutoff valve.

9. A fuel shutoff device according to claim 8, wherein said fuel shutoff controller includes an amplifying circuit connected between said computing circuit and said fuel injection valve, and a switching circuit connected to said amplifying circuit and responsive to said fuel shutoff signal for deenergizing said amplifying circuit thereby to close said fuel injection valve simultaneously with said shutoff valve.

10. A fuel shutoff device according to claim 9, wherein said amplifying circuit includes a plurality of transistors. 

1. A fuel shutoff device for an internal combustion engine having throttle valve and adapted for shutting off the fuel supply to said engine during deceleration to reduce carbon monoxide and hydrocarbon contents in exhaust gases emitted from said engine, said fuel shutoff device comprising, in combination, a throttle valve position detector having means operatively associated with said throttle valve for generating a voltage signal corresponding to the position of said throttle valve, a fuel shutoff signal generator responsive to said voltage signal from said throttle valve position detector for generating a fuel shutoff signal, said fuel shutoff signal generator including a differentiating circuit connEcted to said throttle valve position detector for receiving said voltage signal corresponding to the position of said throttle valve and a monostable multivibrator connected to said differentiating circuit for generating said fuel shutoff signal, said differentiating circuit having means for differentiating said voltage signal in terms of time to render said monostable multivibrator in its quasi-stable state to cause the same to generate said fuel shutoff signal when the time derivative of said voltage signal exceeds a predetermined value during said deceleration, said monostable multivibrator having means to keep the time duration during which said monostable multiple vibrator remains in its quasi-stable state to be long enough to last still after said throttle valve reaches its fully closed position, and a shutoff valve controller connected to said fuel shutoff signal generator and responsive to said fuel shutoff signal to shut off the fuel supply to said engine.
 1. A fuel shutoff device for an internal combustion engine having throttle valve and adapted for shutting off the fuel supply to said engine during deceleration to reduce carbon monoxide and hydrocarbon contents in exhaust gases emitted from said engine, said fuel shutoff device comprising, in combination, a throttle valve position detector having means operatively associated with said throttle valve for generating a voltage signal corresponding to the position of said throttle valve, a fuel shutoff signal generator responsive to said voltage signal from said throttle valve position detector for generating a fuel shutoff signal, said fuel shutoff signal generator including a differentiating circuit connEcted to said throttle valve position detector for receiving said voltage signal corresponding to the position of said throttle valve and a monostable multivibrator connected to said differentiating circuit for generating said fuel shutoff signal, said differentiating circuit having means for differentiating said voltage signal in terms of time to render said monostable multivibrator in its quasi-stable state to cause the same to generate said fuel shutoff signal when the time derivative of said voltage signal exceeds a predetermined value during said deceleration, said monostable multivibrator having means to keep the time duration during which said monostable multiple vibrator remains in its quasi-stable state to be long enough to last still after said throttle valve reaches its fully closed position, and a shutoff valve controller connected to said fuel shutoff signal generator and responsive to said fuel shutoff signal to shut off the fuel supply to said engine.
 2. A fuel shutoff device for an internal combustion engine having a throttle valve and adapted for shutting off the fuel supply to said engine during deceleration to reduce carbon monoxide and hydrocarbon contents in exhaust gases emitted from said engine, said fuel shutoff device comprising, in combination, a throttle valve position detector operatively associated with said throttle valve for generating a voltage signal in proportion to the position of said throttle valve, said throttle valve position detector having an oscillation circuit with a constant oscillation frequency and a d.c. conversion circuit to receive the output of said oscillation circuit by way of a coupling coil, the degree of said coupling coil being changed by a shielding plate which moves as said throttle valve is moved, a fuel shutoff signal generator responsive to said voltage signal from said throttle valve position detector for generating a fuel shutoff signal, said fuel shutoff signal generator including a differentiating circuit connected to said throttle valve position detector for receiving said voltage signal and a monostable multivibrator connected to said differentiating circuit for generating said fuel shutoff signal in response to the output thereof, said differentiating circuit having means for differentiating said voltage signal in terms of time to render said monostable multivibrator in its quasi-stable state when the time derivative of said voltage signal exceeds a predetermined value during said deceleration, said monostable multivibrator having means to keep the time duration during which said monostable multivibrator remains in its quasi-stable state to be long enough to last still after said throttle valve reaches its fully closed position, and a shutoff valve controller connected to said fuel shutoff signal generator and responsive to said fuel shutoff signal to shut off the fuel supply to said engine.
 3. A fuel shutoff device according to claim 2 wherein said differentiating means includes a capacitor connected to said throttle valve position detector and a resistor connected to said capacitor, the joint between said capacitor and said resistor being connected to said monostable multivibrator.
 4. A fuel shutoff device according to claim 2, wherein said means of said monostable multivibrator includes a capacitor and a resistor connected thereto.
 5. A fuel shutoff device for an internal combustion engine having a throttle valve and adapted for shutting off the fuel supply to said engine during deceleration thereof to reduce carbon monoxide and hydrocarbon contents in exhaust gases emitted from said engine, said fuel shutoff device comprising, in combination, a fuel shutoff valve, a throttle valve position detector operatively associated with said throttle valve for generating a voltage signal in proportion to the position of said throttle valve, a fuel shutoff signal generator responsive to said voltage signal for generating a fuel shutoff signal, said fuel shutoff signal generator including a differentiatinG circuit connected to said throttle valve position detector for receiving said voltage signal and a monostable multivibrator connected to said differentiating circuit for generating said fuel shutoff signal in response to the output thereof, said differentiating circuit having means for differentiating said voltage signal in terms of time to render said monostable multivibrator in its quasi-stable state when the time derivative of said voltage signal exceeds a predetermined value during said deceleration, said monostable multivibrator having means to keep the time duration during which said monostable multivibrator remains in its quasi-stable state to be long enough to last still after said throttle valve reaches to its fully closed position, an engine driven triggering device having means for producing a pulse signal having a repetition rate proportional to engine speed, a fully closed throttle valve detecting switch adapted to be closed when said throttle valve is moved to its fully closed position, a shutoff valve controller having a plurality of inputs connected to said fuel shutoff signal generator, said engine driven triggering device and said fully closed throttle valve detecting switch and an output connected to said fuel shutoff valve, said shutoff valve controller being responsive to said fuel shutoff signal for thereby keeping said shutoff valve closed to interrupt delivery of fuel to said engine.
 6. A fuel shutoff device according to claim 5, wherein said throttle valve position detector includes an oscillation circuit having a constant oscillation frequency and d.c. conversion circuit adapted to receive the output of said oscillation circuit by way of a coupling coil, the degree of coupling of said coupling coil being changed by a shielding plate which moves as said throttle valve is moved.
 7. A fuel shutoff device according to claim 6, wherein said shutoff valve controller includes a driving circuit having an input connected to said fuel shutoff signal generator and an output connected to said shutoff valve, first and second switching circuits connected to said engine driven triggering device, said first switching circuit being responsive when said pulse signal exceeds a value corresponding to a first predetermined engine speed, and said second switching circuit being responsive when said pulse signal exceeds a value corresponding to a second predetermined engine speed, and a flip-flop circuit having a plurality of inputs connected to said first and second switching circuits and said fully closed throttle valve detecting switch and having an output connected to said driving circuit for controlling said driving circuit in response to said pulse signal and the output from said fully closed throttle valve detecting switch for thereby controlling actuation of said shutoff valve.
 8. A fuel shutoff device according to claim 6, further comprising a fuel injection valve communicating with said fuel shutoff valve, a computing circuit connected to said engine driven triggering device to calculate a proper pulse width of an injection pulse for actuating said fuel injection valve in response to said pulse signal from said engine driven triggering device, and a fuel shutoff controller having inputs connected to said computing circuit and said fuel shutoff signal generator and an output connected to said fuel injection valve, said fuel shutoff controller being responsive to said fuel shutoff signal for thereby closing said fuel injection valve simultaneously with said fuel shutoff valve.
 9. A fuel shutoff device according to claim 8, wherein said fuel shutoff controller includes an amplifying circuit connected between said computing circuit and said fuel injection valve, and a switching circuit connected to said amplifying circuit and responsive to said fuel shutoff signal for deenergizing said amplifying circuit thereby to close said fuel injection valve simultaneously with said shutoff valve. 